With respect to the HIV infection which is the cause of the acquired immune deficiency syndrome (hereinafter, referred to as AIDS), as well as taking fundamentally preventive measures against HIV infection, in case the suspicion for possible infection arises, it is important to establish a technique which is capable of early diagnosis of the presence or absence of infection.
Further, even when the HIV may seem to have disappeared from the body by treatment, if the detection sensitivity of the virus in diagnostic techniques is low, in spite of the HIV being latent in the body, there is a possibility of misdiagnosis that the HIV has “disappeared” from the body, leaving the root for AIDS recurrence.
In the acute infection period after the HIV infection, the HIV invades into a host cell, reverse transcribes its own viral RNA to synthesize DNA, inserts the DNA into the host cell DNA, and turns into a provirus. In a host cell, the provirus expresses the viral genes and packages the viral RNA with its own viral proteins, thereby forming the virus particles, and the virus particles are going outside the host cell.
Currently, as an anti-HIV therapeutic method in clinical trial, a therapy combining multiple drugs (Highly Active Anti-Retroviral Therapy: hereinafter, referred to as a HAART therapy) is common. The HAART therapy is a method of administering a several kinds of inhibitors that inhibit reverse transcription of the viral RNA, insertion of the viral DNA into the genomic DNA, and the like in the acute infection period as described above. By the HAART therapy, anti-HIV therapies have been achieved a remarkable development.
On the other hand, in the course of treatment with the HAART therapy, a portion of infected cells acquire resistance to the HAART therapy (hereinafter, these infected cells will be referred to as the latently infected cells). In the latently infected cells, in spite of having a provirus, the viral life cycle observed in the acute infection period is at rest, and the viral RNA is not produced. Since the HAART therapy is for inhibiting the steps of the viral replication as described above, elimination of the virus from the latently infected cells by the HAART therapy is difficult. However, if the HAART therapy is interrupted, the life cycle of the virus in the latently infected cells resumes.
Therefore, impossibility of virus removal from the latent infected cells is adversely affecting the quality of life (QOL) of HIV patients.
On the other hand, the inventors of the present invention have found that the latently infected cells produce a short RNA of about 60 bases when a model cell line was constructed and the phenotype of latently infected cells was analyzed by using the model cell lines (see Non-Patent Document 1).
In the method for diagnosing HIV infection, it is important to quantify the viral load in the blood of infected individuals as an index to determine the degree of the condition and the healing process.
Currently, an RNA quantitative method for HIV based on the real-time PCR method as the principle of amplification and detection of target nucleic acids is known as one of the rapid diagnostic methods of HIV infection.
As the RNA quantitative method for HIV using the real-time PCR method, for example, the method described in Patent Document 1 can be mentioned. The method described in Patent Document 1 is a method of amplifying and quantifying the HIV-1 provirus inserted into the genome using degenerate primers designed so as to recognize the various subtypes of HIV-1. Such a method is advantageous in that it can deal not only with the subtype B which is the main source of infection among Japanese infected individuals, but also with a variety of other subtypes.